Convertible power tool

ABSTRACT

A convertible portable power tool has a cylindrical housing for a high-frequency electric motor whose output shaft extends forwardly into bearings provided in a flange which is bolted to the front portion of the housing. The flange has a small outwardly projecting lobe which is connectable with the shells of a plastic central handle. The flange further contains bearings for the shaft or shafts of a reducing gearing which is mounted in front of the flange and serves to drive the input member of a transmission for the tool spindle. The rear end of the motor housing is adjacent to a multi-section cap which contains a reversing device for the motor and is connected by screws to extensions provided on the sections of the handle. Such extensions define a channel for conductors which connect the motor with a switch in the interior of the handle. When the handle is removed and the cap is replaced with a cap which is connected to an energy source and contains an electric switch, the power tool can be used as a handle-free portable hand motor. The prefabricated units of the motor are assembled in accordance with the mechanical assembly technique.

United States Patent 1191 Schilling 51 Jan. 9, 1973 [54] CONVERTIBLE POWER TOOL [75] Inventor: Rainer Schilling, Stuttgart, Germany [73] Assignee: Robert Bosch Gmbll, Stuttgart, Germany [22] Filed: July 14, 1971 I [21] Appl. No.: 162,371

[30] Foreign Application Priority Data Aug. 25, 1970 Germany ..P 20 42 012.6

[52], US. Cl ..3l0/50 [51] Int. Cl. ..H02k 7/14 [58] Field of Search ..3l0/47, 50, 268

[56] References Cited UNITED STATES PATENTS 3,344,291 9/1967 Pratt ..3l0/50 3,519,858 7/1970 Morgansom. ....310/47 3,536,943 10/1970 Bowen ....310/50 3,413,498 11/1968 Bowen ....310/50 3,432,703 3/1969 Sheps ..3l0/50 Germany ..3 10/50 Germany ..3l0/50 Primary Examiner-R. Skudy Att0mey-Michael S. Striker [57] ABSTRACT A convertible portable power tool has a cylindrical housing for a high-frequency electric motor whose output shaft extends forwardly into bearings provided in a flange which is bolted to the front portion of the housing. The flange has a small outwardly projecting lobe which is connectable with the shells of a plastic central handle. The flange further contains bearings for the shaft or shafts of a reducing gearing which is mounted in front of the flange and serves to drive the input member of a transmission for the tool spindle. The rear end of the motor housing is adjacent to a multi-section cap which contains a reversing device for the motor and is connected by screws to extensions provided on the sections of the handle. Such extensions define a channel for conductors which connect the motor with a switch in the interior of the handle. When the handle is removed and the cap is replaced with a cap which is connected to an energy source and contains an electric switch, the power tool can be used as a handle-free portable hand motor. The prefabricated units of the motor are assembled in accordance with the mechanical assembly technique.

9 Claims, 2 Drawing Figures CONVERTIBLE POWER TOOL BACKGROUND OF THE INVENTION The present invention relates to power tools in general, and more particularly to improvements in portable power tools. Still more particularly, the invention relates to improvements in convertible portable power tools.

Portable power tools can be classified according to their intended use as well as according to the presence or absence and/or the configuration and location of their handles. Portable power tools without handles are known as fractional motors or hand motors and those with handles can employ a pistol grip handle, a spade type handle or a central handle.

When a particular power tool is to be manufactured in large numbers, the housing is preferably provided with an integral handle of desired size or shape. For example, the housing for the motor of a portable power tool can consist of two halves each of which is provided with an extension or shell. When the two halves of the housing are assembled, the shells constitute a pistol grip, a spade type or a central handle. However, when severaltypes of portable power tools are to be manufactured in short series, it is uneconomical to provide each type of tool with a speciallydesigned handle. The molds or forms for theproductionof complex housings with integral or detachable handles are very expensive and, the making of discrete molds for complex molded or cast housings with integral or separable handles for several discrete power tools contributes excessively to the initial cost if the power tools are produced in small series. On the other hand, the versatility of a power tool is enhanced and its sales appeal is improved considerably if it can be rapidly converted from a power .tool with handle into a so-called hand motor or fractional motor which does not have a handle. This holds true for a-wide variety of power tools, such as drilling or boring machines, torque and impulse transmitting machines for the introduction or removal of screws or bolts and/or for rapid penetration of drills into a wall or the like.

It is already known to employ for the production of portable power tools several mass manufacturing techniques, such as assembling different types of power tools from several components parts or units at least some of which can be used interchangeably in several types of portable machines. Thus, a mass-produced electric motor with its housing can be assembled with different types of reducing gearings, transmissions and tool holders to constitute a portable power drill, a

portable power operated screw driver, a portable power operated hammer drill or the like.

In accordance with the presently prevailing practice, a powertool is provided with a motor housing which is integral with a handle orwhich is without any handle. A drawback of the first technique is that the housing cannot be-used in so-called hand motors because the handle cannot be removed. Another drawback of the first technique is that, if the motor is ahigh-frequency mometallic handle since the latter is integral with the housing. Such metallic handles cannot be used in all types of portable power tools because it is often-desirable or imperative to employ in power tools handles with satisfactory electrically and/or thermally insulating tor, it must comprise a metallic housing and hence a characteristics. A drawback of the second technique is that the means for detachably securing a handle to the motor housing extends well beyond the housing so that such securing means interferes with the manipulation of the housing when the latter formspart of a so-called hand motor and also that the securing means adversely affects the appearance of the housing when the handle is detached.

SUMMARY OF THE INVENTION An object of the invention is to provide a novel and improved portable power tool which consists of separable units at least some of which can be used for'the assembly of a variety of power tools so that they can be manufactured in large numbers even though a particular type of power tool must be furnished in relatively small quantities.

Another object of the invention is to provide a socalled hand motor or fractional motor which can be rapidly converted into one or more types of portable power tools with handles, or vice versa.

A further object of the invention is to provide a portable power tool with novel and improved means for attaching to the motor housing a separable handle and with improved means for facilitating the assembly of the motor housing with one or more different transmissions or other units for conversion into a power tool which is suited for carrying out a specific operation.

An additional object of the invention is tof'achieve economies in the manufacture of portable power tools which must be furnished in short series and which are convertible for use with or without a handle.

A further object of the invention is to provide a convertible power tool which can be produced and assembled in accordance with the mechanical assembly technique. J

The improved tool is preferably assembled of a plurality of prefabricated units in accordance with -the mechanical assemblytechnique. Such units include a main unit composed of a housing and an electric motor mounted in the housing and having a rotary output member extending forwardly beyond the front portion of the housing, an intermediate member or flange secured to the housing adjacent to its front portion and having bearings for the output member and a relatively short outwardly projectinglobe, and a handle which preferably consists of several separable sections or shells made of synthetic plastic material and is separably connected to the lobe of the intermediate member by one or more threaded fasteners.

When the handle is detached, the remaining parts of the power tool can be used as a handle-free fractional motor.

The novel features which are considered as characteristic of the invention are set forth in particular in the appended claims. The improved power tool itself, how ever, both as to its construction andits mode of operation, together with additional features and advantages thereof, will be best understood upon perusal of the following detailed description of certain specific embodiments with reference to the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a partly side elevational. and partly central longitudinal sectional view of a power tool-which embodies the invention; and

FIG. 2 is a rear end elevational view of the power tool as seen from the right-hand side of FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The portable power tool of FIG. 1 is assembled of several mass-produced units and is assumed to constitute a torque and impulse transmitting device, for example, a device serving to drive screws or bolts into or 10 to remove screws or bolts from workpieces. The power tool comprises a first unit including a substantially cylindrical housing 1 for a reversible electric highfrequency motor 2 having an output shaft 7 which extends forwardly beyond the front portion of the housing 1 and is separably coupled to and drives a reduction gearing 3. The latter drives a transmission 4 (not specifically shown) in a separate housing or case 9. The output member of the transmission 4 drives a tool spindle 5 which is connectable with a tool, e.g., with a screwdriver.

An intermediate member or flange6 is mounted in front of the motor housing 1 and includes the front antifriction bearing 6a for the shaft 7 and the rear antifriction bearing (not shown) for the rotary shaft or shafts of the reduction gearing 3. The latter is mounted in a housing or casing 8 which is located between the flange 6 and the case 9 for the transmission 4. The units including the parts 6, 8 and 9 are secured to the housing 1 by elongated screws 10 or analogous threaded fasteners.

The lower portion of the flange 6 is provided with an integral projection or lobe 11 having a tapped bore 12 which is normal to the motor shaft 7. The lobe 11 extends radially outwardly beyond the housing 1 through a distance which is a small fraction of the diameter of the housing 1.

A separately produced central handle has two mirror symmetrical sections or shells 13, 14 (see FIG. 2) which preferably consist of synthetic plastic material. The sections 13, 14 define at the lower end of the handle an opening for a sheath 16 which surrounds an electric cable serving to connect the motor 2 with a source of electrical energy. The cable 15 is secured to the shell 13 by a clamp 17. its conductors are connected to the terminals of an electric switch 18 which is installed in the handle and has a pivotable actuating member 19 extending forwardly through recesses provided in the shells l3 and 14. The switch 18 is connectable with the motor 2 by insulated conductors 18a which extend along the underside of the housing 1 and are concealed by rearwardly projecting extensions 13', 14 of the shells l3, 14. The extensions l3, 14' define a channel for the conductors 18a.

The rear portion of the housing 1 supports a cap which consists of two sections or shells 20, 21 and encloses a reversing device 22 for the motor 2.

The section 13 of the handle is secured to the lobe ll of the flange 6 by a screw 23 which extends into the tapped bore 12. The section 13 is further provided with three integral internally threaded sleeves 24 for screws 25 which hold the sections 13 and 14 together. The section 21 of the cap at the rear end of the housing 1 overlaps the rear ends of the extensions 13', 14'. Two screws 26 connect the sections 20, 21 of the cap with the extensions l3, l4, and two additional screws 27 serve to connect the sections 20, 21 to the housing 1.

The handle including the sections lfi, 14 can be rapidly separated from the flange 6 by removing the screws 23, 26 and 27. The lobe ll of the flange 6 extends only slightly beyond the outline of the housing 1 so that, upon removal of the handle and upon replacement of the cap 20, 21 with a different cap (not shown) which is connected with a cable and contains an electric switch, the remaining units of the power tool can be used as a hand motor or fractional motor. Such versatility or convertibility is of considerable advantage to the purchaser of the power tool.

However, the improved power tool also exhibits many important advantages to the manufacturer. The housing 1 and the motor 2 constitute a main or base unit which can be used as a component of many types of fractional motors (without handles) or as a component of power tools which are provided with a handle. If desired, the power tool can be furnished with a spare flange which can replace the flange 6 and does not have a projection or lobe. Such spare flange can be produced at a minimal cost.

The material of the sections 13, 14 is preferably a synthetic plastic substance which does not conduct electric current and is a good insulator against heat.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can, by applying current knowledge, readily adapt it for various applications without omitting features which fairly constitute essential characteristics of the generic and specific aspects of my contribution to the art and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the claims.

What is claimed as new and desired to be protected by Letters Patent is set forth in the appended.

1. In a power tool which is assembled in accordance with the mechanical assembly technique, a combination comprising a housing having a first end portion and a second end portion remote from said first endportion; an electric motor mounted in said housing and having a tool-driving rotary output member extending 1 byeond said first end portion of said housing;a hollow first intermediate member adjacent to said first end portion and located outside of said housing; a tool supporting member adjacent to said first intermediate member and being remote from said housing; first fastener means separably securing said housing to said first intermediate member and said tool supporting member to said first intermediate member; a second intermediate member connectable. with said housing upon detachment of said first intermediate member, one of said intermediate members having an external projection; a handle; and second fastener means for separably securing said handle to said projection of said one intermediate member.

2. A combination as defined in claim 1, further comprising a reduction gearing having rotary shaft means receiving torque from said output member, said one intermediate member being disposed between said gearing and said housing and having bearing means for said shaft means.

3. A combination as defined in claim 1, wherein said handle comprises a plurality of separable sections consisting of synthetic plastic material.

4. A combination as defined in claim 1, wherein said projection has a tapped bore whose axis is normal to the axis of said output member, said fastener means having external threads extending into said bore.

5. A combination as defined in claim 1, wherein said handle has an extension outwardly adjacent to said housing and extending to said second end portion thereof.

6. A combination as defined in claim 5, further comprising a cap adjacent to the second end portion of said housing and means for connecting said cap to said extension.

7. A combination as defined in claim 6, wherein said handle is hollow and said extension defines a channel,

and further comprising electric conductor means extending from the interior of said handle, through said channel and said cap and to the motor in said housing.

8. A combination as defined in claim 7, wherein said motor is reversible and further including a device mounted in said cap and operable to reverse the direction of rotation of said output member.

9. A combination as defined in claim 1, wherein said projection of said one intermediate member extends beyond the outline of said housing and substantially radially of said output member through a distance which is a small fraction of the maximum transverse dimension of said housing. 

1. In a power tool which is assembled in accordance with the mechanical assembly technique, a combination comprising a housing having a first end portion and a second end portion remote from said first end portion; an electric motor mounted in said housing and having a tool-driving rotary output member extending byeond said first end portion of said housing; a hollow first intermediate member adjacent to said first end portion and located outside of said housing; a tool supporting member adjacent to said first intermediate member and being remote from said housing; first fastener means separably securing said housing to said first intermediate member and said tool supporting member to said first intermediate member; a second intermediate member connectable with said housing upon detachment of said first intermediate member, one of said intermediate members having an external projection; a handle; and second fastener means for separably securing said handle to said projection of said one intermediate member.
 2. A combination as defined in claim 1, further comprising a reduction gearing having rotary shaft means receiving torque from said output member, said one intermediate member being disposed between said gearing and said housing and having bearing means for said shaft means.
 3. A combination as defined in claim 1, wherein said handle comprises a plurality of separable sections consisting of synthetic plastic material.
 4. A combination as defined in claim 1, wherein said projection has a tapped bore whose axis is normal to the axis of said output member, said fastener means having external threads extending into said bore.
 5. A combination as defined in claim 1, wherein said handle has an extension outwardly adjacent to said housing and extending to said second end portion thereof.
 6. A combination as defined in claim 5, further comprising a cap adjacent to the second end portion of said housing and means for connecting said cap to said extension.
 7. A combination as defined in claim 6, wherein said handle is hollow and said extension defines a channel, and further comprising electric conductor means extending from the interior of said handle, through said channel and said cap and to the motor in said housing.
 8. A combination as defined in claim 7, wherein said motor is reversible and further including a device mounted in said cap and operable to reverse the direction of rotation of said output member.
 9. A combination as defined in claim 1, wherein said projection of said one intermediate member extends beyond the outline of said housing and substantiaLly radially of said output member through a distance which is a small fraction of the maximum transverse dimension of said housing. 